Electromagnet



No Model.)

P. B. COREY. BLEOTROMAGNET.

No. 541,471. Patented June 25, 1895.

UNTTED STATES PATENT OFFICE,

FRED BRAINARD COREY, OF BOSTON, MASSACHUSETTS.

ELECTROMAGNET.

SPECIFICATION forming part of Letters Patent No. 541,471, dated June 25,1895.

Application filed April 15, 1895. Serial No. 545,760l- (No model.)

To all whom it may concern.-

Be it known that I, FRED BRAINARD COREY, a citizen of the United States,residing at Loston, in the countyof Suffolk and State of Massachusetts,have invented certain new and useful Improvements in Electromagnets, ofwhich the following is a specification.

My invention relates to electro magnets designed for actuating apparatusin which a me chanical movement is effected by electrical means, andespecially to such apparatus as requires that this movement shall bemade slowly, as is ordinarily accomplished by means of a solenoid whoseaction upon an iron core or plunger is retarded by a dash-pot.

The objects of this invention are to provide a means for producing thedesired movement of the apparatus and to retard this movement so that itshall be effected gradually without the interposition of a dash-pot andthus to lessen the cost of manufacture of the actuating device ormagnet.

The invention is especially applicable to automatic rheostats andsimilar apparatus.

- My invention consists of an electro magnet having segmental annularpole surfaces, an armature revoluble about the axis of said annular polesurfaces, the ends of said armature being in close proximity to saidpole surfaces, pieces of magnetizable metal loosely fitted into recessesin either end of said armature, and a spring tending to oppose theaction of the magnet in turning the armature so as to place its centerline parallel to the axis of the magnetizing coils.

In the accompanying drawings, which illusirate the invention, Figure 1is a plan of the apparatus, partially in section, as preferablyconstructed, while Fig. 2 is a side elevation of the same.

A A represent a piece of iron, preferably a casting, which forms thecore of the magnetizing coils O, C, and at the same time serves as asupport for the other portions of the device or mechanism.

13,13 are the pole pieces of the magnet, which are preferably shaped asshown, secured to the core A A by the screws Z), and whose pole surfacesB, B are concentric with the shaft or spindle E which supports thearmature D, and is in most cases firmly fastened thereto. F is a stopagainst which the armature D is normally held by the spring G. Thisspring is adjustable by means of the thread H and the nut I, or anysimilar device. In either end of the armature D are recesses J, Jcontaining pieces K, K of magnetizable metal which are loosely fittedtherein.

The operation of my invention is as follows: With no energizing currentin the coils O, O, the apparatus will be in the position shown in thedrawings. IV hen current is admitted into the coils O, O through thewires ac and cd, and the coils become energized, the magnetic circuitwill be as follows: Through the core A A, the pole piece 13, the polesurface 3, through the intervening air space to the ar mature D, throughthe air space to the pole surface B of the pole piece B, and thence tothe core A A forming a closed circuit. The magnetizable portions of thecircuit will at once tend to move in such manner as to decrease thereluctance or magnetic resistance of the circuit, and hence themagnetizable pieces K, K will move into contact with the polar surfacesB B and will be held against these surfaces with a force depending upontheir size and form and also upon the mag netic flux through them. Forthe same reason the armature will tend to rotate about the center of theshaft or spindle E, in the direction indicated by the arrow L, and toplace itself parallel to the axis of the magnetizing coils O, O. Thismotion of the armature will be in opposition to the tension of thespring G, and will be retarded by the friction of the parts K, K againstthe polar surfaces I) B It has been found by experiment that it ispossible so to regulate the tension of the spring G and the friction ofthe parts K, K against the polar surfaces B, B as to cause the movementof the armature to be gradual, which is the nature of the movementdesired. The adjustment of the friction is effected by a properformation of the parts K, K. Now, when from anycause the flow of currentin the energizing coils C, O is interrupted, the spring G willimmediately return the armature D to its former position, as shown. Themechanism that is to be actuated by this magnet will be made fast to thearmature D, either directly or through its shaft or spindle E.

Having described the operation of and the results secured by myinvention, I declare that what'I claim is" r 1. In an electro magnethaving segmental pole surfaces the combination with a revolublearmature, of pieces of magn etizable metal loosely fitted into recessesin the said armature, in such manner as to be drawn into contact withthe said pole surfaces when current is admitted to the energizingcoils,'and retard the movement of the armature, as and for the purposeset forth.

2. An electro magnet having segmental pole surfaces, a pivoted armaturehaving its ends in close proximity to the said pole surfaces FREDBRAINARD COREY.

Witnesses:

ARTHUR W. CRossLEY, O. L. COREY.

